High-frequency (HF) surgical devices of the type addressed herein are well-known. They have an HF generator and at least one surgical instrument having an active electrode that is connected to the HF generator via a wire for supplying a high-frequency current. In addition, a neutral electrode is provided, which is likewise connected to the HF generator via a corresponding second wire for returning the current.
An HF generator of the type addressed herein generates a high-frequency electrical voltage or current and routes them to the connected surgical instrument via an appropriate wire. The surgical instrument may be a monopoloar, bipolar or quasi-bipolar instrument for cutting and/or coagulating biological tissue. In addition, accessory devices for adjusting, monitoring, controlling, limiting and/or modulating the HF voltages, HF currents, electric arcs between an active electrode and a biological tissue that are required for cutting and/or coagulating, may be connected to the HF generator or be disposed within it.
However, requirements that are reflected for example, in the European Parliament's Directive 2004/40/EC of 29 Apr. 2004, governing the minimum specifications for protecting the health and safety of employees against hazards due to physical interference (e.g., electromagnetic fields), are associated with such HF surgical devices. In the case of HF surgical devices, the requirements mandate that the wires that lead to a patient be provided with shielding in order, among other things, to minimize the electrical fields arising due to the high-frequency current. A generic HF surgical device with shielded wires is disclosed in DE 91 17 217 U1. In this case, however, the use of shielded wires for connecting the surgical instrument to the HF generator, or for connecting the neutral electrode to the HF generator, is disadvantageous because it is associated with significant problems.
The use of shielded wires gives rise, in particular, to the problem that the shield forms a capacitive load that reduces the level of the output voltage between the surgical instrument and the tissue to be treated. This is unfortunate because the level of the high-frequency voltage present between the active electrode and the tissue to be treated is a decisive parameter for the desired HF surgery effect. Moreover, it is necessary, or specified by the pertinent standards, to provide what is known as a decoupling capacitor in the HF generator's output circuit to suppress the occurrence of direct current components that may be harmful to the patient.
Furthermore, using shielded wires also gives rise to the problem that the shielding of the wires is preferably grounded (also referred to as “earthed” or “earth grounded”) and this ground connection promotes the occurrence of leakage currents at points where the patient is in contact with grounded, conductive parts; in particular, these leakage currents may become greater, which in turn has an adverse impact on the surgical effect and also represents a risk to the patient.